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4.56 x 30s / 31s?

Y

yossarian19

NAXJA Forum User
Location
Grass Valley, CA
Has anyone tried running these gears? I know most guys are running 4.56s for 33 inch tires, but I'm at stock gearing and with 30s performance on Utah mountain roads is so bad I'm dropping to SECOND before topping some of them - acceleration at 2000 RPM DOESNT EXIST.. I'm thinking 4.10s should keep me in 3rd but I gotta wonder, with a trailer behind me, should I go even a step further?
Anyone with experience driving big Western hills, the 10% grades that go for 2 miles you know what I mean? Anyone have advice for this?

Have searched - not finding the advice I'm lookin for...
Please help!
-Tom
 
i used to run 4.88's and 31's for hwy and 32's for off-road and never had a problem with any of the mountain roads in this state though it was a bit low for a hwy driver so i don't see why 4.56's wouldn't be a problem
 
I ran's and 30's/4.10's and loved it. It was slightly on the low side, but I really liked it. I would imagine that 31's and 4.56's would be very similar.
I don't think that 30's and 4.56's would be very good if you were on the highway very much.

Hale
 
Have not had time to trim for my new 33s yet, so I'm currently running my half-worn 235x75s with 4.56 gears and it's really not bad at all. I've got oh, 1600-1700 miles on them so far, including a 600 mile trip pulling our pop-up on the highway. Taching around 2,600 at 65 in OD.

Acceleration is great, even pulling the trailer. I really think I will miss the power when the 33s go on and regret not going 4.88s.

I would not hesitate to recommend 4.56s for 31s, especially if you are in mountaineous country and/or tow regularly.
 
I run 4.88's & 33's on my '93. It is a manual, is loud, and I think 4.56's might be more appropriate but I'm planning on 35's and geared accordingly. On the other hand, I run 4.10's & 235's (29's) on my '98 with an automatic and I love the power. It is very fast. It does rev a little high when doing 84mph on the interstate though.
 
I have a 98' 4.0, AW4, NP231 and I am running 4.56's and 31's and a pair of true tracs and I love it. Great power for towing and its pretty quick also. I spend about 2 weeks a year in the Colorado Rockies every fall and it does really well. The first year I did it open diffs on 31's and 3.55's and it was horrible. The 4.56's made a BIG difference in power. With my current setup I can cruise all day at 70mph (around 2700rpm) and still average 18-20mpg on the highway and I average 15 in the city. My highway fuel mileage stayed pretty close to the same as it was with the 3.55's but I do get a little better in-town mileage now with the 4.56's.
 
Thanks all for the input. Got all the info I think I need / now the issue is "how big is this jeep going to get and when?" 4.10s won't do for 33s but neither will stock suspension...
Anyhoo. Thanks.
 
Ben H said:
That gearing would be awesome.
Click to expand...

Yes, it was. I got around the mpg as Racer-X. JIM.
 
i'm running 4.56s with 31's.. it's my daily... been to moab several times, colorado, assorted road trips and i think it's perfect gearing... i put a lot of miles on yearly... plus 33's aren't going to be a problem if i decide to go that way... and my gas mileage has been better than expected especially lately as i've been keeping the speed down to 60 which has upped the MPGs from 15ish to 17 and as high as 19...
 
I've got 30s, well they are technically 29.3" according to the tire maker but my performance here in Colorado with 3.55s is fine.

If you have the 4.0 I think you should do some engine upgrades/tune ups before throwing money at gearing. If you have the 2.5 four popper I would do the gearing like you suggested.

I have the works done to my engine in terms of intake/exhaust except a K&n because they let dirt in.
 
WobblesXJ said:
I like 4.56's with 31's. I originally got 4.56s because I planned on 33's but now I'm thinking I may go to 4.88s for 33s.
Click to expand...

not sure what you're running there WobblesXJ but if i'm not mistaken, 4.56s are as deep as you can go on stock (8.25 & d30 setup not sure on the d35)...
 
(sorry for post the last two were posted at the same time) assume most know this, keep in mind you guys running 8.25s 4:56 is it on that rear carrier if you want a deeper gear its means a 8.8 or 44 is in the future
 
WobblesXJ said:
I like 4.56's with 31's. I originally got 4.56s because I planned on 33's but now I'm thinking I may go to 4.88s for 33s.
Click to expand...

I now have the 3.55 on 31's and it bites the big one.

I am planning 4.88 and 33's My jeep only sees 2000 miles per year. I want more grunt for the 4.0/aw4. I am hoping to spend more time in OD while on the freeway to and from the trail head. There will be a shore period of time when I have 4.88 and 31's. That will be interesting.
 
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